A VHF/UHF tuner 10 for receiving television (TV) signals as a conventional high-frequency device will be described. As shown in FIG. 7, the VHF/UHF tuner 10 includes a VHF section and a UHF section. Since the sections are almost the same in structure, the VHF section will be explained. The VHF section includes input terminal 1 for receiving the TV signals, low-pass filter (LPF) 2a coupled to input terminal 1, tuning filter 3a coupled to an output of LPF 2a, high-frequency amplifier 4a coupled to an output of tuning filter 3a, inter-stage filter 5a coupled to an output of high-frequency amplifier 4a, mixer 7a having an input port coupled to an output of inter-stage filter 5a and another input port coupled to an output of local oscillator 6a, intermediate-frequency amplifier 8 coupled to an output of mixer 7a, and output terminal 9 coupled to an output of intermediate-frequency amplifier 8.
The UHF section includes high-pass filter 2b instead of low-pass filter 2a in the VHF section. That is, filters 2a and 2b separates the received signals into VHF signals and UHF signals. Other than this are substantially identical to each other between the two sections except for handling frequencies of different bandwidths. For simple explanation, components of the UHF section commonly used in the VHF section are denoted by corresponding reference numerals with a subscript “b”. Input terminal 1, intermediate-frequency amplifier 8, and output terminal 9 are shared between the two sections.
The aforementioned circuits are formed on a printed circuit board, and are accommodated, as shown in FIG. 8, in metallic shield case 10. To avoid interference between circuits, these circuits are isolated from each other by metallic partitions 11a, 11b in high frequencies.
Partition 11a is located between tuning filters 3a, 3b and inter-stage filters 5a, 5b, and more specifically, located above transistors in high-frequency amplifiers 4a and 4b. If outputs from high-frequency amplifiers 4a and 4b return upstream, abnormal oscillation may occurs. Partition 11a is inserted to avoid the inconvenience.
Partition 11b is located between local oscillators 6a, 6b and inter-stage filters 5a, 5b. Partition 11b blocks leakage of signals generated by local oscillators 6a and 6b through input terminal 1 to the outside, which may affects other televisions. For designing a device that uses public radio waves with others, it is important to avoid affecting others. The leakage of signals is thus double-blocked by partitions 11b and 11a. 
In order to block the leakage and radiation of undesired high frequencies, partitions 11a and 11b are made of metal, and isolates electrically and mechanically between the circuits. In particular, mechanically isolated, the circuits include components which are limited in their arrangement.